TESEO: 30 days of benznidazole was non-inferior to 60 days with fewer adverse events

Design

Open-label, randomised, non-inferiority phase 2b trial, three sites in Bolivia

Population

450 adults aged 18 to 50 with chronic T cruzi infection; 435 in mITT

Primary outcome

Sustained parasitological clearance by qPCR to 36 months; drug-related adverse events

Effect

Benznidazole 30 days 94% vs 60 days 95%; risk difference -2.0 (97.5% CI -5.41 to 1.45); adverse events 37% vs 60%

TESEO was an open-label, randomised, non-inferiority phase 2b trial at three Bolivian sites. It enrolled 450 adults aged 18 to 50 with qPCR-confirmed chronic Trypanosoma cruzi infection, indeterminate or early cardiac form. Six arms compared standard 60-day benznidazole or nifurtimox with 30-day and 90-day variants. Of 435 in the modified intention-to-treat population, sustained parasitological clearance up to 36 months was 95% (69 of 73) with the 60-day benznidazole standard and 94% (68 of 72) with benznidazole 150 mg once daily for 30 days.

The longitudinal analysis supported non-inferiority for all four experimental arms (for the 30-day benznidazole arm, risk difference -2.0, 97.5% CI -5.41 to 1.45; margin -9.5 points). Drug-related adverse events occurred in 37% (28 of 75) with 30-day benznidazole against 60% (45 of 75) with the 60-day standard (risk difference -23 points, 95% CI -38 to -7). Most events began within 10 to 14 days whatever the duration.

The authors suggest 30-day benznidazole as the preferred regimen, but state that phase 3 trials of long-term efficacy across parasite genotypes and settings are needed before guidelines change. Guidelines have not changed.

• Current guidelines have not changed; do not shorten treatment on this trial alone.
• Discuss the finding with specialist services that treat Chagas disease, particularly where adverse events cause interruption.
• Most drug-related adverse events appeared in the first 10 to 14 days, so review patients early.
• The trial enrolled adults aged 18 to 50 with indeterminate or early cardiac disease, so it does not speak to older or advanced patients.
• Nifurtimox 30- and 90-day arms met non-inferiority but had wide intervals.

Why it matters

Treatment interruption from adverse events is the main limit on Chagas therapy, and this trial finds a way of reducing it without a measurable loss of efficacy.

Don't overread it

A phase 2b trial in Bolivian adults with indeterminate or early cardiac disease, using PCR clearance, does not show clinical cure or benefit in advanced cardiomyopathy.

The statistics, in plain English

Non-inferiority means the shorter course was not worse than the standard by more than 9.5 percentage points. With about 72 patients per arm, that margin is wide, and clearance was measured by PCR, which is a surrogate for cure. The nifurtimox comparisons have much wider intervals than benznidazole.

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